1. Field of the Invention
The present invention relates to an implant for the closing of defect openings in the body of a human or animal and to a system for the placement of such an implant.
In particular in the treatment of vascular disorders, in order to reduce the risk of complications and reduce the trauma for patients caused by major operations it has been endeavoured for years to treat vascular defects by minimally invasive surgery. In such surgery, the site to be treated is not opened directly by an operation but instead instruments and implants are introduced through relatively small incisions, in particular into the abdominal cavity. In cardiology, treatment is preferably carried out by means of catheters, which are introduced into the vascular system at a suitable location, in particular via the major arteries of the leg. In this so-called interventional treatment, instruments and implants are introduced through the catheters or sheaths in order to perform the interventions.
In particular for the treatment of septal defects of the heart, interventional treatment offers enormous advantages, since it is not necessary to open the thorax and cut open the heart, which is sensitive and difficult to stop.
For this purpose, the prior art discloses a series of implants and catheter systems with which implants for the closure of defect openings can be introduced into the body and placed at the site of the defect.
2. Description of the prior art
An implant of the type mentioned at the beginning and a catheter system for the placement of such an implant are described in WO 97/28744. In this document there are also a large number of references to further literature and a discussion of U.S. Pat. No. 5,108,420 A, DE 42 22 291 A1, DE 28 22 603 A, U.S. Pat. No. 5,108,420 A and WO 96/01591.
Furthermore, WO 93/13712 discloses an implant for the closure of septal defects which in the implanted state assumes a double-cone or double-disc configuration, the outer structures respectively being formed by wire elements which are not directly connected to one another and are covered with fabric membranes, with the fabric membranes being sewn together in a radius corresponding to the defect to be closed. A major disadvantage of this system is that the implant constructed from a plurality of structural elements requires considerable effort for its assembly, in particular since the diameter of the sewn region has to be adapted to the diameter of the septal defect to be closed. Mass production instead of complex one-off fabrication could only be achieved if large quantities of such implants with graduated diameters of the sewn seams were produced surplus to immediate requirements and kept in stock. It goes without saying that such a course of action would not necessarily be economically advantageous in comparison with one-off assembly, since an enormous number of implants which may never be used would have to be stored at delivery depots and the like.
In WO 95/27448 there is a description of an implant which is to be used as a vein filter and for which it is also proposed that it be used as a load-bearing structure for a septal closure. In this case, a relatively elongated double cone is formed from a series of individual wires, the cones being directed towards each other in the manner of a bone in one configuration and being made to point in the same direction, similar to a fly agaric toadstool, in a further configuration.
U.S. Pat. No. 5,433,727 A discloses an implant in which a type of umbrella is placed in front of a septal defect and is secured through the defect by a counter-closure, which is essentially formed by four loops respectively produced by a wire, which unfold when ejected from a catheter and are intended to prevent the implant from slipping through to the umbrella side.
Finally, EP 0 474 887 A1 discloses an implant in which two round or otherwise polygonally shaped sealing patches, which are respectively stretched out by a peripheral compliant frame element, are connected inter alia by means of a multiplicity of threads, which have to be pulled tight through the catheter for the placement of the implant. In a further embodiment, a central snap closure is to be provided for the positional securement of the two patches. The implant described there is very difficult to place on account of the considerable effort needed for its manipulation and also requires complicated assembly which is very prone to faults.
An implant for the closure of septal defects in particular, with which quite secure placement is possible and with which erroneous seating can be corrected and, if necessary, the implant can be withdrawn again into a catheter until it is finally discharged, is described in the already mentioned WO 97/28744. The implant described there unfolds of its own accord, on account of a secondary structure impressed on it, when it is ejected from the catheter and adapts itself within broad limits to the dimensions of the defect by elastic forces. On account of the structure impressed in the superelastic material described, the parts of the implant arranged in the manner of a double disc on both sides of the septum clamp elastically against the surrounding region of the septum and in this way lead to a particularly secure seating and low leakage, the so-called residual shunt. In this case, the implant is formed by a series of wire-shaped elements, which are connected to one another by suitable joining processes, such as ultrasonic welding or brazing. Finally, the implant is also provided with a covering, which is appropriately fastened to the wire-shaped elements.
If suitable for the treatment of septal defects, all the implants described have the disadvantage that they comprise a plurality of individual parts which have to be assembled or connected to one another by joining processes. This is not a major problem for verifying the functional capability of such an implant and when small numbers are concerned, but is not very expedient for mass production, since the reliable functioning of the connecting locations has to be checked, involving considerable effort in terms of quality assurance, because of the great responsibility which the product entails, and the same applies to the other assembly steps. Voids possibly occurring during the joining processes also harbour the risk that during production they will be colonized by germs, which possibly cannot be reliably killed by sterilization and may be released after prolonged use or if fatigue ruptures occur.